Stepmania Online

I've never played FFR, but I've downloaded some of the packs to play on SMO. I'm not familiar with the difficulty rating of FFR songs, and wondered what the equivalent would be for SMO songs.
For example, if it says the song difficulty is a 4 in an FFR pack, what would that be for SMO?

Typically the difficulty numbers used to describe files are based solely on the discretion of the step artists. In a lot of packs, files may be easier or harder than one another, despite having conflicting difficulty ratings. Sometimes, packs will use a NPS difficulty scale for their files, but for the most part things are a bit unpredictable.

FFR's difficulty system on the website has no bearing on the difficulty ratings of files from FFR community packs, if you were wondering that as well.

Those packs in particular adopted a different grading scale than ddr or itg. It seems like they were trying to go for a keyboard grading scale where a 1 footer would be similar to the hardest pad files. A 10 footer would be at the top end of keyboard difficulty.

The ffr season packs are based on note's per second. I'm not sure about the community packs, because Idk if Gundam_Dude ran those as well or not.

The difficulty is the nps. Oni 9 is 9nps. Heavy 10 is 10nps.